Substrates are often guided in sputter units past a so-called target, from the surface of which particles are sputtered off, which are deposited on the substrate. As the substrates can be utilized, for example, glass plates, which are transported through an inline sputter unit. These glass plates are set into a frame connected with a transport device.
A device for the transport of substrates into and through vacuum treatment units, for example, is known, which comprises a bulky foot part composed of two wheel sets correlated with one track and one support bearing (DE 41 39 549 A1). The substrates to be treated are herein held by means of a rectangular substrate holder.
Furthermore is known an annular substrate holder for the mounting of a round substrate plate, this substrate holder, in turn, being held by four equally distributed holding arms (DE 102 11 827 C1).
If the substrates held in frames have a coefficient of thermal expansion different from that of the frames, the substrates may be covered at the margins nonuniformly and onesidedly to too high a degree. In the case of wafers this is referred to as “edge exclusion”, i.e. to a peripheral region of the wafer which is not coated.
The invention therefore addresses the problem of providing a carrier for substrates, in which the substrates are covered uniformly and not too thickly at the margin.
The problem is resolved according to the present invention, which relates in part to a carrier for a substrate, wherein at least parts of the carrier are comprised of a material having a coefficient of thermal expansion which is higher than the coefficient of thermal expansion of the substrate. To avoid, or at least decrease, nonuniform coating of the substrate at the margins, in particular during sputter processes, a bar is centrally connected with the carrier. This bar has a coefficient of thermal expansion lower than the region of the carrier at which it is fastened.
The advantage attained with the invention resides in particular therein that through the combination of lightweight cost-effective aluminum, which expands to a high degree, with a centering means of a material, which expands to a lesser degree, for example titanium, the “edge exclusion” is reduced.
An embodiment example of the invention is shown in the drawing and will be described in further detail below: